Pie menus are widely used in graphical user interface for performing the selection of an action or for triggering a function. Pie menus are also referred to as radial menus because the menu items are displayed in a substantially circular arrangement around a center point. Each of the menu items, in addition to the icon or text representing the item, has a selectable area that is a pie menu sector, i.e. a sector of the entire pie menu. Pie menus are commonly implemented with a pie menu activation input that starts their operation. Subsequent input may then be interpreted as a pie menu selection input, i.e. an input that selects one of the pie menu sectors. Once a pie menu sector has been selected, usually the action associated with the pie menu item assigned to that sector is executed. The action associated with the pie menu item can be the selection of one value associated with the item, or it can be the triggering of a function, for instance adding texture on a 3D modeled object.
Pie menus suffers several drawbacks. The first one is that user interactions that are not pointer-based can be problematic. Notably, touch screens are problematic because the appendage (e.g. a finger) in contact with the touch screen performs both the position of the user interaction and the user user interaction.
The second drawback is that the selection accuracy in a pie menu is related to the number of items the menu offers. Higher numbers of menu items require more angular precision for selection. For that reason, a pie menu involves a trade-off between the number of menu items and the ease of selection from the menu. This is more particularly an issue in contexts of selection of continuous values (within a range); for instance, the size of a pie menu is limited in order to keep the user working area clear.
A solution to problem is to implement a pie menu wherein each menu item leads to sub-menu items, themselves leading to sub-menus item until the user finds the value he is loocking for. However, this kind of solution is not satisfactory as the successive selections of a menu item go against the principles of operation of a pie menu: a faster and more reliable selection that depends on the distance between the cursor and the menus item, a large menu slices in size and near the pointer for fast interaction, use selection without looking at the menu while performing a selection.
Within this context, there is still a need for an improved method for setting in a pie menu the value of a parameter that is selected among a range of continuous values.